This invention relates to a heat transfer image-receiving sheet, more particularly, to a heat transfer image-receiving sheet which can form a recorded image excellent in color forming density, sharpness and various fastnesses.
Various heat transfer methods have been known in the art, and among them, there has been practiced the sublimation transfer method, in which a sublimable dye is used as the recording agent. The sublimable dye is carried on a base sheet such as paper to provide heat transfer sheet, which is superposed on an image-receiving material capable of dyeing with a sublimable dye, for example, a fabric made of a polyester. The sublimable dye is migrated to the image-receiving material by applying heat energy according to pattern information from the back of the heat transfer sheet.
In the above sublimation transfer method, in the sublimation printing method, when the image-receiving material is, for example, a fabric made of a polyester, heat energy is imparted for a relatively longer time, and therefore the image-receiving material itself is heated by the heat energy imparted, whereby relatively good migration of the dye is accomplished.
However, with the progress in recording methods, when fine letters or figures or photographic images are to be formed on, for example, image-receiving materials having dye receiving layers provided on polyester sheets or papers at high speed by use of a thermal head, etc., heat energy is required to be imparted within a very short time of second units or less. Therefore, within such a short time, the sublimable dye and the image-receiving material cannot be heated, whereby no image with sufficient density can be formed.
Accordingly, in order to respond to such high speed recording, sublimable dyes excellent in sublimability have been developed. However, dyes excellent in sublimability have generally smaller molecular weights, and hence pose problems such as the dyes may be migrated with passage of time in the image-receiving material after transfer, or may be bleeded onto the surface, thus causing disturbance of the image elaborately formed to make them indistinct or contamination of surrounding articles.
In order to avoid such problems, if a sublimable dye having a relatively larger molecular weight is used, the sublimation speed in inferior in the high speed recording method as described above, and therefore no image with satisfactory density can be formed as described above.